PROGRAM SUMMARY Pulmonary vascular disease (PVD) is perhaps the most important complication for children with congenital heart disease (CHD) that results in increased pulmonary blood flow (PBF) and pressure. Postnatally, the presence of large communications at the level of the ventricles (e.g. ventricular septal defect) or great vessels (e.g. truncus arteriosus) exposes the pulmonary circulation to abnormal elevations in blood flow and pressure, which results in progressive structural and functional abnormalities of the pulmonary vasculature. Metabolic reprogramming is increasingly recognized as a critical component of early pulmonary vascular injury and disease. Vascular morphology studies in our Shunt lamb model demonstrate a >2-fold increase in pulmonary arterioles in Shunt compared to control lambs. This is opposed to the decrease in arterial counts demonstrated in humans with advanced disease. This early increase in angiogenesis likely represents an adaptation to the increase in flow and pressure. The development of a hyperproliferative, anti-apoptotic endothelial phenotype is necessary for this angiogenic response. Further, it requires a dramatic metabolic reprogramming that serves to supply these cells with the necessary biosynthetic precursors required for cell division while simultaneously decreasing cellular ATP levels due to increased consumption and decreased respiration. We have linked this decrease in ATP to the loss of hsp90-mediated NO signaling and the development of endothelial dysfunction and vascular remodeling. Thus, this PPG intensely focuses on increasing our understanding of: i) the differential effects of mechanical forces on cellular metabolic programming; ii) post translational modifications (PTMs) that influence key signaling pathways involved in metabolic reprogramming; iii) interactions between mitochondrial network dynamics, metabolism, and cellular survival; iv) how these pathways interact to disrupt hsp90-mediated NO signaling; and v) novel therapeutic strategies for treating CHD with increased PBF. The key novel pathways that comprise the focus of each Project were identified by our intensive investigations into the metabolic reprogramming underlying the development of pulmonary vascular disease and selected for their capacity to contribute to a spectrum of cellular responses related to glutaminolysis and aerobic glycolysis (Project #1), cellular -oxidation and mitochondrial bioenergetics (Project #2), mitochondrial network dynamics and mitophagy (Project #3), and cell proliferation and apoptosis (Projects #1 & #3). Investigations are integrated across our three PPG projects to fully understand how metabolic reprogramming leads to the loss of hsp90- mediated NO signaling and represents the thematic underpinning of this PPG. The synergy derived from the interactions between individual Projects and scientific Cores, with our programmatic approaches, will promote an increased understanding of how mechanical forces modify cell metabolism, NO signaling and endothelial function, and the development of novel, individualized therapies to attenuate pulmonary vascular disease in children born with CHD that result in increased PBF and pressure.